Upgrading gasoline and naphtha



Patented Oct. 26, 1954 UPGRADING GASOLINE AND NAPHTHA Alex G. Oblad, Springfield, and Heinz Heinemann,

Drexel Hill, Pa., Corporation, of Delaware assignors to Houdry Process Wilmington, DeL, a corporation N 0 Drawing. Application December 29, 1950, Serial No. 203,544

4 Claims.

1 This application is a continuation-in-part of our application Serial No. 198,468, filed November 30, 1950.

The present invention relates to improvements in catalytic reforming of hydrocarbon distillates boiling approximately in the range of gasoline and is particularly concerned with novel catalysts of high selectivity for use in such process and the particular method of preparation by which such catalysts may be obtained.

One of the principal objects of the invention is the provision of an improved catalyst capable of producing high yields of gasoline of desired enhanced octane quality and of good lead susceptibility, while minimizing the occurrence or extent of such other accompanying reactions, such as cracking, which tend to produce coke and low molecular weight hydrocarbon gases, at the expense of desired gasoline yields.

In previous known processes for upgrading gasoline and naphtha fractions, involving treatment at superatmospheric pressure and in the presence of added hydrogen, catalysts have been employed having the property of promoting dehydrogenation reactions, the best known being molybdenum oxides on activated alumina. While under the conditions employed in these previous processes dehydrogenation of naphthenes present in the gasoline charged to reforming does take place, other simultaneous reactions occur to substantial extent, including cracking of parts of the charge, resulting in the formation of significant quantities of low molecular weight hydrocarbon gases accompanied by deposition of coke in sufficient amounts to limit the practical on-stream operating period to about 4-8 hours, followed by regeneration of the catalyst. The reported butane-free gasoline yields from such processes are in the order of about 70-80% by volume of the charge. In other related processes conditions were employed to dehydrogenate selected narrow cuts of naphthenic materials to aromatic hydrocarbons, operating under conditions obtaining lower conversion of the charge per pass, and generally at higher pressures (up to about 50-70 atmospheres) than the previously described process. In these processes operating at lower conversion levels longer on-streamperiods of up to several sible, requiring as much as about 20-24: hours for regeneration of the coke produced. Reformed products high in aromatic content are stated to be obtained, but the overall gasoline yields are not substantially better than those obtained in days or more might be pos- 1 the previously described processes carried out at lower pressure.

In accordance with the present invention, naphthenes in gasoline and naphtha fractions, are selectively converted to aromatics under conditions'disfavoring accompanying production of undesirable side products such as coke and gas. This desirable result is brought about by carrying out the reforming process in the presence of a catalyst consisting essentially of a minor proportion of molybdenum oxide Well distributed over the available surface of an alumina carrier which has been previously treated to render the carrier substantially devoid of cracking or polymerizing-promoting function. Such catalysts are prepared in accordance with the invention by treating alumina with magnesium compounds which are converted to magnesia, the conditions of treatment being controlled to avoid formation of so called beta alumina. This treatment results in the production of an alumina base or carrier having no significant cracking activity. Molybdena is then incorporated in the specially prepared carrier in known or suitable manner. 7

The catalyst thus prepared is employed in reforming of gasoline and naphtha distillates in the presence of added hydrogen, at pressure of 200-1000 p. s. i., temperatures between about 850-1000 the hydrocarbon distillate being charged at a liquid space rate of preferably not less than 1 volume per hour per volume of catalyst. Preferred operating conditions include temperatures not in excess of about 950-975 F. and liquid space rates of at least 2.

The catalysts employed in the reforming processes of the invention are highly selective in promoting dehydrogenation of naphthenes but have little or no activity in promoting cracking of hydrocarbons. The selectivity of various catalysts can be tested by their separate effects on conversion of heptane and of methylcyclohexane under standardized conditions. The catalysts of the invention as contrasted with typical commercial dehydrogenation catalysts of the molybdena-alumina type or catalysts of the chromealumina type, are characterized by high rates of conversion of methylcyclohexane to aromatics Without accompanying production of large amounts of by-products such as coke and gas and by their relatively low activity in the conversion ofnormal heptane. Since dehydrocyclization of normal heptane involved is associated with a course of reaction including a cracking function, the characteristic behavior of the catalysts of the 3 invention is indicative of high selectivity for promoting dehydrogenation of hydroaromatic naphthene compounds without material tendency to promote accompanying side reactions such as carbon-carbon scission and polymerization.

Activated alumina of commerce as well as heat-treated bauxite already possesses significant cracking activity. By the incorporation of molybdena in known manner in such aluminaceous carriers the cracking activity of the composite may be further increased. In the catalysts of the present invention, however, the cracking promoting function of the carrier .is materially attenuated or destroyed, to provide the desired selectivity for dehydrogenation.

The reforming process of the invention is applicable to the treatment of various "naphtha charge stocks containing naphthenes of the hydroaromatic type, including catalytically cracked distillates as well as straight run gasoline and inaphthas and id'istillates from thermal cracking. An important application of the invention :is in the treatment of gasoline and naphtha fractions nerivedfrom hydrogenative processes such ias-hy- .drogenative cracking and destructive hydrogenation, which fractions .are generally characterized by .a high naphthene content-and low octane rat- It .is important that the magnesia :be incorporated .in the alumina prior to therincorporation of the molybdena. Catalysts prepared by treatment of molybd'enaealumina withmagnesia do not have the .same high selectivity of the catalystsof the invention and characteristically obtain lower .gasoline yields and gproduce significantly larger quantities of coke than the catalysts of the .invention. This observed difference ;in behavior-of the tWocatalysts-can not be entirely satisfactorily explained. The reason'th-at knownhydroforming catalysts comprising molybdena on activated alumina tend .to produce .coke :and low :molecular weight gases appears to be .related to cracking activity. .The.crackingapromotingifunctionisabelieved to .be centered on .acid sites existing :in these cataysts or is related to their ability to accommodate .or transfer protons. By base-exchanging or treating such activesites with appropriate cations the acidity or protonic actiw-ityandaccordingly'the cracking function can be inhibited.

.The catalysts .of the invention-are prepared by treating calcined or activated alumina in .lump or .tabletform with anaqueous solution-of aasoluble magnesium compound and drying the product. The efiect .of this treatment .is {already noticeable when as little .as 0.05% magnesia is incorporated in thealumina; quantities'of mag-- nesiaabove. about .2-3 do not appear-tohaveany added useful effect andmay be undesirable. Pref-- erably about 0.1 to 2.0% magnesia by weight is employed.

Thedried magnesia-alumina isdipped in a solution of a molybdenum salt, such as ammonium molybdate, and the salt decomposed to the-oxide. The molybdena may be present .in proportions of about 7.0 to 15.0% .by weight of the .finaLcatalyst. .It is important that the alumina, before .orlafter deposition of the molybdenum compound, .be not heated to high temperatures or otherwise treated to cause transformation thereof .to .beta forms of alumina.

Prior to being placed on-s'tream the catalyst is treated in a stream of reducing gas. such as hydrogen to transform the molybdenum .ox'ides .toLlower valence state.

EXAMPLE I Commercial activated-alumina tablets (Harshaw) Were treated with 20 magnesium chloride (MgClz) solution, using about 5 liters solution per kilogram of alumina, then washed free of chlorides and dried. The dried product :was treated for thirty minutes with a solution of ammonium molybdate (calculated to deposit 10% M003 on the alumina) containing about 270 grams M003 ;p.er liter'of water, in the proportions of about 400 milliliters solution per kilogram of alumina. The treated product was drained, dried, and heat treated at 1050 for two hours. Before being placed on stream, hydrogen was passed over the catalyst to reduce the molybdena to lower valence Fforms. Thefinal catalyst contained 0.28% MgO.

The catalyst thus prepared was employed in reforming East Texas naphtha with the following results:

Table 1 .Ch%rge.zEastTexaslnaphtha.

Catalyst: M00 on magnesia-treated alumina.

An .AlzOa-.MgO-.M0.0s catalyst was 1prepared following the procedureof the .precedingexample using about the same proportions ofcomponenbs, and likewise teste in reforming the previously "reported .naphtha .in a series'of runs with ,thelfollowing results: Table .2 a

Operating conditions:

ZPressure, p. s. i. g 600 .600 Temp, F "950 950 LSV,(v0l.Ihr;/.vol. :2 l A Hz: oil ratio 3 .3 Yields:

:Gaso. (05+), .vol. percent 82.18 84. 8 04, vol. percent .i 11.2- 10. 1 Dry fGas, percent 4.; '4. 0 Blake, wt. percent (0c; :0." 2 Octanes:

-,,CF;R-R clear -87.-"8 88:6 -+8,cc.-TEL .1 {:6

:Oloviously many modifications and variat'ionsof the invention as :hereinbefore set forth =may be made without departing from'therspirit and'seope thereof, and therefore only such limitations should be imposed .as are indicated :inthe zappendedclaims.

We claimas our invention:

'1. ,The method of up rading the -\quality of .a naphtha fraction containing .naphthenic hydro:- carbons boiling in the range .of gasoline, which comprises contacting such .afractionin the presence of added hydrogen with a catalyst consistin'g'of molybdenum oxideincorporated inaninert "non-acidic carrier consisting essentially .of gamma alumina containing up to about 3% amorphous magnesia incorporated therein and being substantially free o'f crystalline magnesium aluminate, said :catalyst'having been prepared by incorporation of the molybdenum oxide into' the alumina carrier which has .beenapreviously impregnated with magnesia; :said rconta'cting'i'being performed under conditions suitable for dehydrogenation of naphthenes in said fraction, including super atmospheric pressure and temperatures in the range of 850-1000 R; and recovering a gasoline fraction of desired boiling range from the reformate thus distributed.

2. The method of selectively dehydrogenating naphthenic hydrocarbons in a hydrocarbon fraction boiling approximately in the range of gasoline with concomitant formation of minimized quantities of cracked products including coke and low molecular weight hydrocarbon gases, which comprises contacting said hydrocarbon fraction with a catalyst consisting of about 7-15% by weight of molybdenum oxides incorporated in an inert non-acidic carrier consisting essentially of gamma alumina containing .05-3% amorphous magnesia incorporated therein said carrier being substantially free of crystalline magnesium aluminate, said catalyst having been prepared by incorporation of the molybdenum oxide into the alumina carrier which has been previously impregnated with magnesia; said contacting being effected under reaction conditions including pressure of 200 to 1000 pounds per square inch, temperatures of about 850-1000 F., and liquid space velocity not less than 1 volume hydrocarbon fraction per hour per volume of catalyst.

3. The method of obtaining high yields of gasoline of improved octane rating which comprises charging a naphtha out having a high naphthene content to catalytic dehydrogenation in the presence of a catalyst consisting of 7-15% by weight molybdenum oxides distributed on a carrier composed of gamma alumina containing 0.1-2% amorphous magnesia distributed therein, said catalyst having been prepared by incorporation of the molybdenum oxide into the alumina carrier which has been previously impregnated with magnesia, and effecting selective dehydrogenating of naphthenes in said out in contact with said catalyst at a temperature in the range of 850- 950 F., under a pressure of about 200-1000 pounds per square inch, hydrogen in excess being added to said naphtha charge, and said naphtha being charged to said dehydrogenation at a liquid space rate in excess of 1 volume per hour per volume of catalyst.

4. The method of selectively dehydrogenating naphthenic hydrocarbons contained in a gasoline fraction without production of excessive quantities of cracked products including coke and low molecular weight hydrocarbons, which comprises contacting such a gasoline fraction with a catalyst consisting of molybdenum oxide incorporated in an inert non-acidic carrier consisting essentially of gamma alumina containing up to about 3% amorphous magnesia incorporated therein and being substantially free of crystalline magnesium aluminate, said catalyst having been prepared by incorporation of the molybdenum oxide into the alumina carrier which has been previously impregnated with magnesia; said contacting being performed under dehydrogenation conditions including temperature in the range of 850-950 F., pressure of about 1200-1000 p. s. i., and a liquid space velocity of at least 2 volumes of hydrocarbon charge per hour per volume of catalyst.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,371,087 Webb et al. Mar. 6, 1945 2,378,208 Fuller et a1 June 12, 1945 2,556,280 Kearby June 12, 1951 

1. THE METHOD OF UPGRADING THE QUALITY OF A NAPHTHA FRACTION CONTAINING NAPHTHENIC HYDROCARBONS BOILING IN THE RANGE OF GASOLINE, WHICH COMPRISES CONTACTING SUCH A FRACTION IN THE PRESENCE OF ADDED HYDROGEN WITH A CATALYST CONSISTING OF MOLYBDENUM OXIDE INCORPORATED IN AN INERT NON-ACIDIC CARRIER CONSISTING ESSENTIALLY OF GAMMA ALUMINA CONTAINING UP TO ABOUT 3% AMORPHOUS MAGNESIA INCORPORATED THEREIN AND BEING SUBSTANTIALLY FREE OF CRYSTALLINE MAGNESIUM ALUMINATE, SAID CATALYST HAVING BEEN PREPARED BY INCORPORATION OF THE MOLYBDENUM OXIDE INTO THE ALUMINA CARRIER WHICH HAS BEEN PREVIOUSLY IMPREGNATED WITH MAGNESIA; AND CONTACTING BEING PERFORMED UNDER CONDITIONS SUITABLE FOR DEHYDROGENATION OF NAPHTHENES IN SAID FRACTION, INCLUDING SUPER ATMOSPHERIC PRESSURE AND TEMPERATURES IN THE RANGE OF 850-1000* F.; AND RECOVERING A GASOLINE FRACTION OF DESIRED BOILING RANGE FROM THE REFORMATE THUS DISTRIBUTED. 